Wide Field Fundus Camera with Auto-Montage at A Single Alignment

ABSTRACT

A wide field fundus camera is disclosed to implement multiple illumination beam projectors and to capture multiple retinal images at various viewing angles to facilitate wide field retinal examination. The wide field fundus camera contemplates an ultra-wide field lens that can provide edge to edge imaging of the entire retina at a single alignment. It also contemplates configuration of said multiple illumination beam projectors to provide visualization of retina and Purkinje reflections simultaneously to facilitate determination of proper camera alignment with the eye. It further contemplates control of multiple illumination beam projectors in a programmable manner to capture said multiple retinal images. It further contemplates a real-time algorithm to reduce said reflected and scattered light haze in said retinal images. It further contemplates automated montage of said multiple retinal images into a single wide field FOV retinal montage and automated removal reflected and scattered light haze from said retinal montage.

CLAIM OF PRIORITY

This application claims benefit of priority of U.S. Provisional PatentApplication No. 62/352,944, Yates et al., titled “Wide Field FundusCamera with Montage at a Single Alignment,” filed on Jun. 21, 2016,which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present subject matter relates to a wide field fundus camera forphotographing subject retinas.

BACKGROUND

Retinal images are broadly used for diagnosis of various diseases of thehuman retina. For instance, various retinal cameras have been routinelyused to screen and to detect three of the most common eye diseases inadults: diabetic eye disease, glaucoma, and age-related maculardegeneration. Early detection of these diseases can delay and preventsubsequent loss of vision. Conventional retina cameras used to performthese screening exams typically have a central 45 to 60-degree field ofview (FOV) representing less than 10% of the entire surface area of theretina.

In contrast, wide field retinal images, referring to a greater than60-degree FOV, are commonly used in the diagnosis of retinopathy ofprematurity (ROP), a retinal disease of premature infants. At advancedstages, ROP can result in retinal detachment with permanent vision lossbut is often treatable with early routine screening and detection.Traditionally, ROP is typically diagnosed via manual physician examusing an indirect ophthalmoscope. The examining physician utilizesindirect ophthalmoscopy, and relies on scleral depression to visualizethe retinal periphery to the ora serrata over eight cardinal positions(12, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, and 10:30). Given thatpathology associated with ROP occurs predominantly in the retinalperiphery, a minimum 120-degree FOV of the retina is required for properdiagnosis. Traditional screening and diagnosis of ROP require a highlyskilled ophthalmologist to perform this exam and correctly documenthis/her retinal findings. It is a time-consuming process, and it lacksreliable documentation, with most ophthalmologists still performingsketched drawings to represent their retinal findings.

Wide field retinal images in a digital format can be obtained with theRetcam from Clarity Medical Systems (Pleasanton, Calif., United Statesof America). In one approach, a wide field fundus camera employs anillumination ring as shown in U.S. Pat. No. 5,822,036 (Massie et al.)located at the tip of a handpiece housing the illumination light source,imaging optics and camera sensor. The illumination ring is formed with abundle of optical fibers and projects bright illumination through theentire pupil. The device provides uniform illumination over a field ofview to produce a retinal image with a 120-degree FOV of the retina. Useof such a configuration may lack clarity in the image when thecrystalline lens is less transparent and when the Purkinje reflectionimages from the crystalline lens surfaces become visible inside thefield of view. Use of such a configuration may be suitable for newbornbabies and infants with a highly transparent crystalline lens but may beless suitable for patients with a less transparent lens, in particular,adults.

Furthermore, sufficient retinal examination for ROP detection requiresan edge to edge observation of the entire retina, i.e., to cover an180-degree FOV. The entire retina occupies an ocular hemisphere. An180-degree FOV refers to a field of view that encompasses this entireocular hemisphere. A 130 degree FOV device will require a tilt of +/−25degrees to reach the retinal edge. Imaging of the entire retina withthis 130-degree FOV device will necessarily require 6 to 8 separateimages with the camera placed at multiple tilt positions relative to thecentral axis of the eye to image the entire edge of the retina.Sufficient retinal examination with a 130-degree FOV device istime-consuming, and correct tilt alignment of the device with the eyefor edge to edge imaging of the retinal periphery to detect ROP remainsdifficult, even for a well-trained ophthalmologist.

SUMMARY

Newborn babies and infants may have a less-transparent crystalline lens,due to various clinical conditions. Image haze may appear due to lightscattering inside the cornea or less-transparent crystalline lenswherever the illumination beam path overlaps with imaging beam path.This image haze may also stem from Purkinje reflection images fromcorneal (i.e. Purkinje I and II) and crystalline lens surfaces (i.e.,Purkinje III and IV). We refer to image haze as scattered or reflectedlight off any ocular or camera surface, other than the retina, whereinthis scattered or reflected light can reach the recording sensor of aretinal camera.

Image haze may be improved by optical techniques separating theillumination beam path from the image beam path inside the crystallinelens. This configuration can be found in conventional retinal cameras,but with a limit on the field of view of 45 to 60 degrees and withvarious masks on the illumination beam path to create an image windowthroughout the crystalline lens. However, such a configuration remains achallenge to implement for a wider field of view fundus camera.

Another highly desirable feature for fundus cameras would be a quick andreliable autofocus. Unlike conventional tabletop fundus cameras, a widefield fundus camera for ROP screening is typically a handheld device,and thus fast response of the camera may improve the usability of thedevice. Generally, autofocus found in conventional tabletop funduscameras is much slower than found in consumer image recording devices.There have been prior attempts to implement a consumer image recordingdevice with fast autofocus into a handheld fundus camera.

In US patent application publication US 2012/0229617, titled “Hand-HeldPortable Fundus Camera for Screening Photography,” Yates et al. disclosehow to implement a consumer image recording device into a handheldfundus camera to utilize autofocus mechanisms built into a consumercamera. Another concern is the reliability as autofocus in consumerimage recording devices may rely on well-illuminated, and high contrastfeatures to perform, while retinal images may lack such well-illuminatedand high contrast features. In US patent application publication US2013/0335704, titled “Intuitive Techniques and Apparatus for OphthalmicImaging,” Yates et al. disclose how to project a diffractively-modifiedlaser beam to create well-illuminated and high contrast features on theretina to enhance auto focusing. A further challenge arises as to how toimplement the concept with non-coherent light and how to improveperformance through less-transparent crystalline lenses.

Auto focusing and imaging through a less-transparent crystalline lensremains a challenging issue for wide field fundus cameras with a widefield of view. Instrumenting an indirect ophthalmoscope into a digitalformat and adapting a consumer image recording device and its fastautofocus have yet to be implemented for wide field fundus cameras.

An example according to the present subject matter contemplates a widefield fundus camera to implement multiple illumination beam projectors,of which each illumination beam projector mimics the illuminationconditions of an indirect ophthalmoscope. An example according to thepresent subject matter thus contemplates taking multiple retinal imagesat various viewing angles to mimic viewing conditions of the indirectophthalmoscope. An example according to the present subject matter alsocontemplates implementing a wide field fundus camera with an imagerecording device that enables autofocus, auto exposure, real-timedisplay and wireless transfer of high definition images. An exampleaccording to the present subject matter further contemplates projectinga narrow slit beam at an angle to enhance autofocus through aless-transparent crystalline lens. An example according to the presentsubject matter also further contemplates implementing a broad slit beaminto each of multiple illumination beam projectors to better imagethrough a less-transparent crystalline lens. An example according to thepresent subject matter contemplates positioning of said multipleillumination beam projectors in axially symmetric positions around acentral viewing axis. A further example according to the present subjectmatter contemplates coupling said multiple illumination beam projectorsto a central viewing axis using a beam splitter or mirror. An exampleaccording to the present subject matter further contemplatesimplementing an illumination beam projector that can simultaneouslyilluminate the retina and provide Purkinje reflections within thewide-field FOV to facilitate simultaneous visualization of the retinaand Purkinje reflections to determine camera alignment with the eye. Afurther example according to the present subject matter contemplatesmultiple axially symmetric illumination beam projectors to illuminatethe retina and provide Purkinje reflection within the wide-field FOV tofacilitate axial centration of the camera with the eye. An exampleaccording to the present subject matter further contemplatesimplementing image processing to stitch multiple retinal images into anevenly exposed single field image.

To achieve edge to edge observation of the entire retina at a singlealignment, an ultra-wide FOV lens of 180 degrees is highly desirable. Anexample according to the present subject matter contemplatesimplementing a contact lens system (i.e., a lens having a surface tocontact an eye) with a 160-degree FOV or wider. The contact lens systemcomprises one or more aspherical surfaces. The term “ultra-wide FOV”refers to 160 degrees FOV or wider.

For ultra-wide FOV imaging, reflections (i.e., Purkinje I and II) andscattering haze from the cornea become unavoidable. An example accordingto the present subject matter contemplates placing all the Purkinjereflections into clusters of scattering haze and to allow removal ofsaid Purkinje reflections and scattering haze with digital masks. Afurther example according to the present subject matter contemplatesplacing Purkinje reflections into clusters of scattering haze by one ormore of the following: adjustment of the angle of the illuminationprojector beam with the visual axis, adjustment of illuminationprojector beam shape, or adjustment of illumination projector beam spotsize). A further example according to the present subject mattercontemplates placing Purkinje reflections into clusters of scatteringhaze by one or more of the following: adjustment of said wide-angle orultra-wide angle FOV lens aspherical surface curvature or lens aperture.

Image haze in retinal images differs fundamentally from diffuseatmospheric haze in outdoor photos. Retinal image haze is directional,produced by scattering of the incident illumination used to examine theeye, has different scattering characteristics depending on which ocularsurface is being illuminated by this light (cornea, lens, iris), hasdifferent polarization characteristics, has different spatialcharacteristics depending on the position of the scattering surface, andhas different spectral characteristics from atmospheric haze. While thegeneral problem of removing atmospheric haze from photographic imageshas been previously considered (eg U.S. Ser. No. 12/697,575), thesemodels assume an orthogonal relationship between the illuminating source(eg. the Sun) creating the scattering light as compared to the cameraphotographing the image and the object being photographed. Mathematicalmodels of such haze conditions generate unique solutions for removinghaze from outdoor images that are not optimized for reduction orelimination of retinal image haze. Estimating a haze map for retinalimages requires consideration of the characteristics of the illuminationsource and the scattering surfaces of the eye which generate this imagehaze.

A further example according to the present subject matter contemplatesdigital removal of reflection and scattering haze through identificationof characteristics of the reflection and scattering haze component todifferentiate it from the retinal image of the image. An exampleaccording to the present subject matter contemplates determination ofthe reflection and scattering haze component of the sectional image, asopposed to the retinal component, using one or more differentiatingfeatures that include spectral, positional, shape, size, sharpness,uniformity, detail, directional, and distribution pattern of saidreflection and scattering haze created by said illumination beamprojectors. A further example contemplates optical modeling of expectedhaze pattern from a directed light source as provided by saidillumination beam projector to further assist in identification ofreflection and scattering haze. A further example contemplates automatedidentification of Purkinje reflections in captured retinal images toassess camera alignment with an eye to allow prediction of expectedreflection and scattering haze to further facilitate removal ofreflection and scattering haze.

Removal of reflection and scattering haze can facilitate photographervisualization of retinal detail to determine the presence of retinalpathology, determination of camera centration and tilt with respect tothe central visual axis of the eye, and determination of retinal focusby the camera prior to capture of a retinal image. In PCT/US2015/049950,Yates et al contemplated removal of reflection and scattering hazefollowing acquisition of sequential images. An example according to thepresent subject matter contemplates real-time removal of reflection andscattering haze to permit retinal camera positioning and retinal imagecomposition prior to retinal image capture. We refer to real-time asremoval of reflected and scattering haze in less than 200 millisecondsto allow display of de-hazed retinal images on an image display at arate greater than five frames per second. An example according to thepresent subject matter contemplates display of de-hazed retinal imageson an image display at a frame rate greater than or equal to 30 framesper second during alignment of the wide-field camera with the eye, priorto sectional retinal image capture.

Removal of scattering haze can facilitate visualization of Purkinjereflections. Purkinje reflections can be used to determine the alignmentof the camera with respect to the central axis of the eye. An exampleaccording to the present subject matter contemplates removal ofreflection and scattering haze, except for discrete Purkinjereflections, to maximize visualization of said discrete Purkinjereflections to improve assessment of camera alignment with the eye.

Removal of reflection and scattering haze on captured retinal images canfacilitate the creation of a wide-field full FOV image with enhancedimage clarity to allow examination of retinal pathology. An exampleaccording to the present subject matter contemplates reflection andscattering haze removal on sectional retinal images following retinalimage capture. An example according to the present subject mattercontemplates use of digital masks to remove sections of the sectionalimages with prominent purkinje reflections and scattered haze. A furtherexample according to the present subject matter contemplates dehazing ofthe sectional image by estimating and refining a transmission map basedon known characteristics of the reflected and scattered haze and areference retinal transmission map. A further example according to thepresent subject matter contemplates dehazing of the sectional image bydetermining camera alignment with the central axis of the eye using thepattern of Purkinje reflections. Once camera alignment is determined, anestimated haze map is computed using a reference haze model for corneal,iris, and lens reflection and scattered haze for this particularalignment. Sectional images with the reflection and scattering hazeremoved can then be assembled into a single image of full FOV. A furtherexample according to the present subject matter contemplates removal ofresidual reflection and scattering haze removal on the assembled fullFOV single image.

In general a montage image is constructed from individual componentimages to create a wider panorama. This problem has been previouslyconsidered for retinal images. However, proposed algorithms mustnecessarily consider rotational, translational, tilt, and magnificationdifferences inherent in individually acquired retinal images. Generalpanorama stitching algorithms are ill suited to the task given there arefew high contrast retinal features to easily enable determination ofoverlap between images and automatic control point generation used inmontage algorithms. This requires any number of techniques includingskeletonization of the retinal vasculature or searching for optimalspectral frequency overlap between images. There is further a need todetermine which portion of two or more retinal images that overlap todisplay. Finally, there is the general need to blend overlapped imagesto create a seamless border and create the impression of a singleseamless panoramic image. The complexity of this problem frequentlyresults in misalignments between component images in the computedmontage, visible seams between images with a “collage-like” appearanceto the final image, large contrast variation throughout the image, andvery slow processing speed given the number of parameters that must beoptimized when few assumptions can be made about the characteristics ofand relationships between each image. A single montage of 10 images maytake 30 minutes to several hours to generate.

An example according to the present subject matter contemplates toassemble sectional images into a single montage automatically andinstantly. We refer to automatically as not requiring user interventionto generate the full FOV montage from the sectional images. An exampleaccording to the present subject matter contemplates generation of afull FOV montage in less than 5 seconds to allow user review of thecaptured wide-field retinal image to quickly determine the presence ofretinal pathology and the need to capture additional retinal images. Anexample according to the present subject matter contemplates a montagealgorithm that uses one or more simplifying assumptions about thestructure of the sectional images to rapidly generate a single,seamless, well exposed, full FOV montage. These simplifying assumptionsinclude one or more of stereotypical spatial position, image exposure,focus, tilt, specular reflections, illumination pattern, and hazepatterns for these sectional images. These simplifying assumptions allowone or more of automatic determination of sectional image overlap,automatic generation of control points for computing a montage,automatic determination of which sectional image to display inoverlapping areas based on characteristic exposures in each sectionalimage, ability to automatically digitally mask off Purkinje reflectionsand scattering haze based on characteristic haze patterns, generation ofa seamless blend at sectional image overlaps, adjustment of exposurethroughout the montage based on understanding the structure and positionof the illumination beam projector used to take each sectional imagewith respect to the central axis of the eye. An example according to thepresent subject matter contemplates that sectional images are taken witha plurality of illumination beam projectors at high-speed so as tominimize eye movement between each sectional image. If the eye does notmove between each sectional image then it can be assumed that allsectional images are automatically aligned with one another withoutneeding to shift the position of each sectional image when generating afull wide field FOV montage image.

The present invention contemplates the use of an ultra-wide field lensto cover 180-degree FOV. The present invention also contemplatesobtaining centered and on-axis alignment to standardize the haze spotlocations and to stereotype the reflection and scattering haze pattern.The present invention further contemplates real-time dehazing of retinalimages to enable better judgment of proper alignment of the wide-fieldcamera with the eye and proper retinal focus. The present inventionfurther contemplates capture of multiple sectional images of the desiredFOV quickly at a single alignment. The present invention furthercontemplates capture of multiple sectional images to cover an 180-degreeFOV at a single alignment. The present invention further contemplatesdehazing of sectional retinal images to enhance visualization of retinaldetail. The present invention still further contemplates employing anauto-montage algorithm to perform automatic stitching of the sequentialimages into a single montage of the full retinal FOV defined with theultra-wide field lens.

In PCT/US2015/049950, Yates et al contemplated a montage algorithm whereassumed symmetry of retinal illumination and haze in individualsectional images, due to central alignment of the wide field funduscamera with the central axis of the eye, allowed for simplifiedconstruction of the montage image. A further example according to thepresent subject matter contemplates to automatically alter assumedsymmetries and the relationship between sectional images using thecomputed alignment of the wide field fundus camera with respect to theeye. In this manner, the automated montage algorithm can automaticallyand quickly adjust for any central misalignment between eye and widefield fundus camera which might create asymmetries in reflected andscattered haze as well as retinal illumination patterns in sectionalimages. This adjustment would allow for automated and instant montagegeneration to generate a full single wide field FOV even for sectionalimages where the wide field fundus camera is in a non central alignmentwith respect to the eye. In a further example according to the presentsubject matter, asymmetric areas from each sectional image may be usedto generate the wide field FOV montage. In another example according tothe present subject matter, asymmetric digital masks may be generated tomask asymmetric haze in said sectional images to produce said asymmetricareas from each sectional image used to generate the wide field FOVmontage.

Consequently, the present invention contemplates to achieve anauto-montage of sufficient FOV from sequential sectional images taken atany single alignment of the wide field fundus camera with the eye, toimprove usability and improve visualization of retinal details to enabletele-screening of ROP and other retinopathies.

More specifically, an example according to the present subject matterdiscloses a wide field fundus camera, comprising:

-   -   an aspherical lens having a symmetric viewing axis and disposed        to form a retinal image, wherein said aspherical lens is an        element of a wide-field or an ultra-wide field objective lens;    -   an image recording device configured to provide one or more of        auto focus and auto exposure and aligned with said aspherical        lens to capture said retinal image;    -   a first source configured to provide a plurality of illumination        beam projectors positioned around said viewing axis and        projected each at an angle toward said aspherical lens, wherein        two or more illumination beams are arranged in an axial        symmetric configuration relative to the viewing axis to provide        centered and on-axis alignment guidance;    -   a second source configured to provide a narrow illumination beam        projector projected at an angle and away from pupil center to        provide a bright feature on the retina to enhance autofocusing        through less-transparent crystalline lens;    -   cross polarization optics incorporated between said first and        second sources of illumination beams and said image recording        device to reject specular reflections of said illumination beams        and reduce reflected and scattered light haze;    -   a real-time dehazing algorithm implemented to remove reflected        and scattered light from the retina image to facilitate improved        judgment of proper camera alignment with the eye and retinal        image focus;    -   an electronic control circuit configured to provide a system to        control said plurality of illumination beam projectors and        facilitating capture of a plurality of retinal images in a        programmable manner; and    -   an automatic montage algorithm configured to process said        captured plurality of retinal images to mask out hazed areas,        remove reflected and scattered haze, and to stitch the captured        plurality of images into a wide-field or ultra-wide field        composite image.

Therefore, a first aspect of the present subject matter can includeproviding a wide field fundus camera implementing multiple illuminationbeam projectors and multiple retinal images at various viewing angles tomimic retinal examination with an indirect ophthalmoscope. A secondaspect of the present subject matter can include the use of a consumerimage recording device having fast auto focusing so as to make a widefield fundus imaging apparatus quick to respond and easy to use. A thirdaspect of the present subject matter can include the use of a consumerimage recording device having high-speed continuous image capture(greater than five captured images per second) so as to facilitatecapture of multiple sectional images from said multiple illuminationbeam projectors to provide a full FOV prior to movement of the eye. Afourth aspect of the present subject matter can include providing narrowand broad slit beam illuminations to enhance autofocusing and imagingthrough less transparent crystalline lens and reflection haze. A fifthaspect of the present subject matter can include the use of anultra-wide field lens to enable edge to edge detection of the entireretina. A sixth aspect of the present subject matter can include the useof the multiple illumination beams to form guidance for central andon-axis alignment. A sixth aspect of the present subject matter caninclude the use of real-time dehazing to form guidance for central andon-axis alignment. A seventh aspect of the present subject matter caninclude the use of real-time dehazing and automatic montage of capturedsectional retinal images to form a full FOV wide-field orultra-widefield retinal image.

A first aspect of the invention is directed to a wide field funduscamera comprising an objective lens having a viewing axis and disposedto form a retinal image, an image recording device disposed to capturesaid retinal image of said wide field of view, a plurality ofillumination beam projectors positioned around said viewing axis andeach configured to project an illumination beam at an angle toward saidobjective lens, a mechanism of cross polarization configured betweensaid image recording device and said plurality of illumination beamprojectors to reject specular reflections of said illumination beams, animage display operatively coupled to the image recording device todisplay said retinal image from said image recording device, anelectronic controller operatively coupled to said plurality ofillumination beam projectors to provide power to each of the pluralityof illumination beam projectors in a predetermined sequence to provideillumination to obtain each of a plurality of retinal images, and atleast one computing processor programmed to execute a real-time dehazingalgorithm to perform real-time removal of reflection and scattered lighthaze, and at least one computing processor programmed to execute anautomated montage algorithm to produce an automated montage of saidplurality of retinal images into a single image of said wide field ofview.

The camera may further comprise a computing processor programmed toexecute a dehazing algorithm to further remove reflected and scatteredlight haze from said montage image.

In some embodiments, the objective lens is a wide field aspherical lenshaving a FOV of 60 degrees to 160 degrees. The objective lens may be anultra-wide field objective lens having a FOV of 160 degrees or wider.The objective lens may be an ultra-wide field objective lens systemcomprising a contact lens, a meniscus lens and an aspherical lens.

In some embodiments, the plurality of illumination beam projectors areoptically coupled to a plurality of mirrors or beamsplitters to directlight from said projectors along the viewing axis.

In some embodiments, the image recording device is a camera configuredto provide automatic focusing, automatic exposure selection, andcontinuous image capture.

In some embodiments, the real-time dehazing algorithm identifiesreflected and scattered light haze in said retinal images by position ofsaid haze.

In some embodiments, real-time dehazing algorithm identifies reflectedand scattered light haze in said retinal images by spectral content ofsaid haze. The real-time dehazing algorithm may identify cameraalignment with the eye and determines expected reflected and scatteringhaze patterns for this camera alignment to facilitate identification andremoval of said reflected and scattering haze.

In some embodiments, the automated montage algorithm identifies cameraalignment with the eye and combines said plurality of said retinalimages camera into a single full FOV montage for said camera alignment.

In some embodiments, the plurality of illumination beam projectorscomprises 4 projectors positioned to provide four reflection spots at12, 3, 6, and 9 o'clock positions on an eye positioned along the viewingaxis.

In some embodiments, two of said illumination beams are located at the12 and 6 o'clock positions along the viewing axis and two of saidillumination beams are located at the 3 and 9 o'clock positions alongthe viewing axis. In some embodiments, the plurality of illuminationbeam projectors comprises of 8 projectors positioned to provide eightreflection spot clusters at 12, 1:30, 3, 4:30, 6, 7:30, 9, and 10:30o'clock positions on an eye positioned along the viewing axis.

In some embodiments, 4 of the 8 projectors form a first subset providinginfrared illumination and 4 of the 8 projectors form a second subsetproviding white light illumination, each of the first subset and thesecond subset being symmetrically disposed around viewing axis.

The mechanism of cross polarization may be aligned with a polarizationaxis of the eye to reduce reflected and scattered light haze from theeye.

In some embodiments, the illumination beam projectors are configured toprovide simultaneous retinal illumination and visible ocular Purkinjereflections to assess camera alignment with the retina.

In some embodiments, the real-time dehazing algorithm comprisesprocessor accessible instructions for dehazing an image from a widefield fundus camera, that when executed perform acts comprisingcomputing position of purkinje reflections from said wide field funduscamera produced by said illumination beam projectors, computing widefield fundus camera alignment with central axis of eye being imaged bysaid wide field fundus camera using position of said purkinjereflections within said image from said wide field fundus camera,computing an estimated haze map for said wide field fundus image usingreference ocular corneal and lens reflected and scattering haze modelfor said illumination beam projector at said camera alignment with saidcentral axis of a reference model eye, computing a digital mask forremoval of reflected and scattering haze from said wide field fundusimage using estimated haze map, computing a processed masked wide fieldfundus image from said wide field fundus image by removal of portions ofsaid wide field fundus image covered by said digital mask, computing atransmission map utilizing estimated haze map for said wide field fundusimage, refining a transmission map for said wide field fundus imageusing reference retinal wide field fundus image, recovering a retinalimage from said masked wide field fundus image using the refinedtransmission map to dehaze the masked wide field fundus image andproduce a dehazed masked wide field retinal image.

In some embodiments, the real-time dehazing algorithm comprisesprocessor-accessible instructions for dehazing an image from a widefield fundus camera, that when executed perform acts comprisingcomputing an estimated haze map using at least one of a referencespectrum and size and spatial distribution of said reflected andscattering haze, computing a transmission map utilizing estimated hazemap for said wide field fundus image, refining a transmission maputilizing estimated retinal transmission from reference retinal widefield fundus image, recovering a retinal image from said wide fieldfundus image using the computed transmission map to dehaze the widefield fundus image and produce a dehazed wide field retinal image.

In some embodiments, the automated montage algorithm comprises processoraccessible instructions for montaging sectional images from a wide fieldfundus camera into a single FOV wide field fundus image, that, whenexecuted, performs acts comprising computing position of purkinjereflections from said wide field fundus camera produced by saidillumination beam projectors, computing wide field fundus cameraalignment with central axis of eye being imaged by said wide fieldfundus camera using position of said purkinje reflections within saidsectional images from said wide field fundus camera, computing an areaof each said sectional image to be included in said montage image andcreating a sectional image digital mask for each said sectional image toremove scattering haze and Purkinje reflections, determined by said widefield fundus camera alignment, computing a masked sectional image fromsaid wide field fundus camera sectional image by removal of the area ofeach said sectional image covered by each said sectional image digitalmask, computing a blending of overlapping areas of each said sectionalimage using one or more of sectional image exposure, wide field funduscamera alignment, sectional image haze, sectional image focus, sectionalimage spatial frequencies, and sectional image sharpness to preservesaid montage image fine structural detail while evening out said montageimage exposure to create a seamless montage, computing an imageprojection for said montage image by using said wide field fundus cameraalignment to minimize montage image distortion.

Another aspect of the invention is directed to a wide field funduscamera comprising an objective lens having a viewing axis and disposedto form a retinal image, an image recording device disposed to capturesaid retinal image of said wide field of view, a plurality of eightillumination beam projectors positioned symmetrically around saidviewing axis and each configured to project an illumination beam at anangle toward said objective lens, a mechanism of cross polarizationconfigured between said image recording device and said plurality ofillumination beam projectors to reject specular reflections of saidillumination beams, an image display operatively coupled to the imagerecording device to display said retinal image from said image recordingdevice, an electronic controller operatively coupled to said pluralityof eight illumination beam projectors to provide power to each of theplurality of illumination beam projectors in a predetermined sequence toilluminate for each sequential image two of said illumination beamprojectors with said illumination beam projectors positioned 180-degreesfrom one another around said viewing axis, and at least one computingprocessor programmed to execute a real-time dehazing algorithm toperform real-time removal of reflection and scattered light haze; atleast one computing processor programmed to execute an automated montagealgorithm to produce an automated montage of said two or four sequentialretinal images into a single image of said wide field of view, and atleast one computing processor programmed to execute a dehazing algorithmto further remove residual reflection and scattered light haze from saidautomated montage image to create a haze free montage image

In some embodiments, the camera is configure to acquire two sequentialimages using said electronic controller powering two said illuminationbeam projectors positioned in a symmetric matter about the viewing axiswith illumination beam projectors at 12 o'clock and 6 o'clock poweredfor the first sequential image and 3 o'clock and 9 o'clock powered forthe second sequential image. In some embodiments, the two sequentialimages are acquired using said electronic controller powering two saidillumination beam projectors positioned in a symmetric matter about theviewing axis with illumination beam projectors at 10:30 o'clock and 4:30o'clock powered for the first sequential image and 1:30 o'clock and 7:30o'clock powered for the second sequential image. In some embodiments,four sequential images are acquired using said electronic controllerpowering two said illumination beam projectors positioned in a symmetricmatter about the viewing axis with illumination beam projectors at 12o'clock and 6 o'clock powered for the first sequential image, 3 o'clockand 9 o'clock powered for the second sequential image, 10:30 o'clock and4:30 o'clock powered for the third sequential image and 1:30 o'clock and7:30 o'clock powered for the fourth sequential image.

The objective lens may be a wide field aspherical lens having a FOV of60 degrees to 160 degrees. In some embodiments, the objective lens is anultra-wide field objective lens having a FOV of 160 degrees or wider.

In some embodiments, the objective lens is an ultra-wide field objectivelens system comprising a contact lens, a meniscus lens and an asphericallens.

Still another aspect of the invention is directed to a method ofoperating a wide field fundus camera, comprising the steps of providingan objective lens having a viewing axis and disposed to image a retinahaving a fundus, the viewing axis being in first alignment with theretina, providing an image recording device disposed to capture saidretinal image; providing a plurality of illumination beam projectorspositioned around said viewing axis and projected each at apredetermined angle with respect to said viewing axis, providing amechanism of cross polarization configured between said image recordingdevice and said plurality of illumination beam projectors to rejectspecular reflections of said illumination beams; providing an imagedisplay configured to display said retinal image from said imagerecording device, providing a computing processor coupled with saidimage recording device and said image display to enable real-time imageprocessing and display, providing a real-time dehazing algorithmincorporated in said computing processor to perform real-time removal ofreflection and scattered light haze, providing an electronic controllerpowering said plurality of illumination beam projectors in aprogrammable manner, capturing a plurality of fundus images at the firstalignment, each image captured with the plurality of illumination beamprojectors in a corresponding state of illumination, at least two of thestates of illumination being different than one another, and providingan automated montage algorithm incorporated in said computing processorto perform automated montage of said plurality of retinal images into asingle montage image of said wide field of view.

In some instances the plurality of fundus images comprises two images,each of the two images generated using illumination from only acorresponding two, axial-symmetrically disposed illumination beamprojectors of the plurality of illumination beam projectors.

In some instances the plurality of fundus images comprises four images,each of the four images generated using illumination from only acorresponding two, axial-symmetrically disposed illumination beamprojectors of the plurality of illumination beam projectors.

In some instances, the plurality of fundus images comprises four images,each of the four images generated using illumination from acorresponding one of the plurality of illumination beam projectors.

In some instances, the plurality of fundus images may comprise eightimages, each of the eight images generated using illumination from acorresponding one of the plurality of illumination beam projectors.

The method may further comprise a dehazing algorithm incorporated insaid computing processor to further remove reflected and scattered lighthaze from said montage image.

Yet another aspect of the invention is directed to a computer-readablestorage medium including instructions for a dehaze algorithm for a widefield fundus camera comprising processor accessible instructions fordehazing an image from a wide field fundus camera, that when executedperform acts comprising computing position of purkinje reflections fromsaid wide field fundus camera produced by said illumination beamprojectors, computing wide field fundus camera alignment with centralaxis of eye being imaged by said wide field fundus camera using positionof said purkinje reflections within said image from said wide fieldfundus camera, computing an estimated haze map for said wide fieldfundus image using reference ocular corneal and lens reflected andscattering haze model for said illumination beam projector at saidcamera alignment with said central axis of a reference model eye,computing digital mask for removal of reflected and scattering haze fromsaid wide field fundus image using estimated haze map, computingprocessed masked wide field fundus image from said wide field fundusimage by removal of portions of said wide field fundus image covered bysaid digital mask, computing transmission map utilizing estimated hazemap for said wide field fundus image, refining transmission map for saidwide field fundus image using reference retinal wide field fundus image,and recovering retinal image from said masked wide field fundus imageusing the refined transmission map to dehaze the masked wide fieldfundus image and produce a dehazed masked wide field retinal image.

Still another aspect of the invention is directed to a computer-readablestorage medium including instructions for a dehaze algorithm for a widefield fundus camera comprising processor accessible instructions fordehazing an image from a wide field fundus camera, that when executedperform acts comprising computing estimated haze map using at least oneof reference spectrum and size and spatial distribution of saidreflected and scattering haze computing transmission map utilizingestimated haze map for said wide field fundus image, refiningtransmission map utilizing estimated retinal transmission from referenceretinal wide field fundus image, and recovering retinal image from saidwide field fundus image using the computed transmission map to dehazethe wide field fundus image and produce a dehazed wide field retinalimage.

Yet another aspect of the invention is directed to a computer-readablestorage medium including instructions for an automated montage algorithmfor a wide field fundus camera comprising processor accessibleinstructions for montaging sectional images from a wide field funduscamera into a single FOV wide field fundus image, that when executedperform acts comprising computing position of purkinje reflections fromsaid wide field fundus camera produced by said illumination beamprojectors, computing wide field fundus camera alignment with centralaxis of eye being imaged by said wide field fundus camera using positionof said purkinje reflections within said sectional images from said widefield fundus camera, computing the area of each said sectional image tobe included in said montage image and creating a sectional image digitalmask for each said sectional image to remove scattering haze andPurkinje reflections, determined by said wide field fundus cameraalignment, computing masked sectional image from said wide field funduscamera sectional image by removal of area of each said sectional imagecovered by each said sectional image digital mask, computing stitchingof said masked sectional images into a single, and computing blending ofoverlapping areas of each said sectional image using one or more ofsectional image exposure, wide field fundus camera alignment, sectionalimage haze, sectional image focus, sectional image spatial frequencies,and sectional image sharpness to preserve said montage image finestructural detail while evening out said montage image exposure tocreate a seamless montage, computing an image projection for saidmontage image by using said wide field fundus camera alignment tominimize montage image distortion, and computing said single FOV widefield fundus image.

These and other aspects of the invention will become more apparent inthe following drawings, detailed description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. illustrates a generally-available camera and related techniquesfor ROP screening.

FIG. 2 shows an illustrative example of a wide field fundus cameraimplemented using multiple illumination beam projectors and a narrowbeam projector.

FIG. 3 shows an illustrative example of a wide field fundus camerahaving one of the multiple illumination beam projectors turned on fortaking one of the multiple retinal images.

FIG. 3B shows an illustrative example of an ultra-wide field funduscamera modified from FIG. 3 that uses an ultra-wide FOV lens. Thewide-field FOV lens in FIG. 3 has been replaced with an ultra-wide FOVlens comprised of a meniscus, contact, and objective lens allowingvisualization of greater than 160-degree FOV of the retina.

FIG. 4 shows an illustrative example of a wide field fundus camerahaving the narrow beam projector turned on to facilitate autofocusingthrough less transparent crystalline lens and reflection haze.

FIG. 5 shows an illustrative example of a wide field fundus camerahaving one of the multiple slit beam projectors turned on to improveimage taking through less transparent crystalline lens and reflectionhaze.

FIG. 6 shows an illustrative example of a handpiece that integrates themultiple illumination projectors, the imaging optics, a consumer imagerecording devices and the contact lens of the wide field fundus camera.

FIG. 7 shows an illustrative example handpiece with Olympus Air A01consumer image recording device placed on a model eye and the resultingretinal image taken by the wide field fundus camera projected wirelesslyover to a tablet.

FIG. 8 shows an illustrative example of the tablet display demonstratingreal-time live view display of the retinal image formed by fourindependent projector beams that may allow proper user alignment withthe eye. Additionally, user controls to set real-time illuminationlevel, photo flash illumination level, the pattern of independentprojector beam illumination control, and independent manual control ofeach projector beam are shown.

FIG. 9 shows an illustrative example of the separate retinal imagesformed by each of four independent projector beams. An image processingmethod may be used to eliminate the lens reflection haze from eachprojector beam and stitch together the clear aspect of the retinal imageto form a final seamless montage that is adjusted to achieve evenexposure across the final montaged image.

FIG. 10 shows an illustrative example of the live-view display formed bythe electronic controller and image recording device at four differentpoints in time. At each point in time, a single independent projectorbeam may be illuminated, with each of four separate independentprojector beams illuminated serially as shown in the four panels. Thedisplay would appear to the user real-time as a rotating illuminationbeam that may allow the user to assess alignment of each illuminationprojector beam with the eye before final image acquisition.

FIG. 11 shows an illustrative example of a photo image of one embodimentof an ultra-wide field fundus camera used to capture an ultra-wide fieldFOV of a baby retina. Four illumination beam projectors are turned onpositioned at 12, 3, 6, and 9 o'clock around said viewing axis. Purkinjereflections and scattering haze are evident. In FIG. 11a no haze removalhas been performed. In FIG. 11b one embodiment of real-time dehazing hasbeen used to partially remove reflected and scattering haze to enhancevisualization of retinal detail.

FIG. 12 shows an illustrative example of two sequential photo imagestaken of a baby retina with an ultra-wide field fundus camera with FIG.12a having illumination beams positioned at 3 and 9 o'clock relative tothe viewing axis turned on. In FIG. 12b illumination beams positionedand 12 and 6 o'clock relative to the viewing axis are turned on.Purkinje reflections and reflected and scattering light haze are evidentin both FIG. 12a and FIG. 12b , with different haze patterns based oncamera alignment with the eye and which illumination beam projectors areturned on.

FIG. 13 shows an illustrative example of an automated montage generatedfrom sequential photo images take of a baby retina with an ultra-widefield fundus camera. FIG. 13a shows an illustrative image of a singleFOV montage generated with real-time dehazing and automated montage fromthe two images of FIG. 12a and FIG. 12b . In FIG. 13a Purkinjereflections as well as reflected and scattering haze have been partiallyremoved to generate a single FOV montage that has enhanced visualizationof retinal detail as compared to FIG. 12a or FIG. 12b . In FIG. 13badditional an additional dehaze algorithm has been performed on thesingle FOV to remove residual haze to further enhance visualization ofultra-wide FOV retinal detail.

FIG. 14a shows an illustrative example of a retinal image needing to bespectrally dehazed.

FIG. 14b shows an illustrative example of a blue channel isolated from aretinal image. It was generated from FIG. 14 a.

FIG. 14c shows an illustrative example of a Gaussian-blurred bluechannel isolated from a retinal image for spectral haze mask creation.It was generated from FIG. 14 b.

FIG. 14d shows an illustrative example of a bias image generated fromthe maximum intensity pixel of a blurred blue channel image. It wasgenerated from FIG. 14 c.

FIG. 14e shows an illustrative example of a transmission mask generatedvia blue channel spectral analysis of a retinal image. It was generatedusing FIG. 14c and FIG. 14 d.

FIG. 14f shows an illustrative example of a retinal image dehazed viaspectral analysis. It was generated from FIG. 14a , FIG. 14c , FIG. 14d, and FIG. 14 e.

FIG. 15a shows an illustrative example of a retinal image demonstratingstereotypical illumination via a single beam illuminator.

FIG. 15b shows an illustrative example of a stereotypical haze patternproduced via blue channel isolation of FIG. 15a . It can be used as amodel for the expected haze pattern resulting from imaging a retinaunder the same camera alignment and illumination conditions.

FIG. 15c shows an illustrative example of the result of an imagethresholding operation used to detect Purkinje reflections. It wasgenerated from FIG. 15 b.

FIG. 16a shows an illustrative example of a retinal image taken withoptimal camera alignment and symmetric illumination via 4 beamilluminators.

FIG. 16b shows an illustrative example of a retinal image taken withincorrect camera alignment, demonstrated via skewed P4 Purkinjereflections and illuminated by 4 beam illuminators. It was taken fromthe same eye as FIG. 16 a.

FIG. 16c shows an illustrative example of P4 reflections detected andisolated from P1 reflections via difference of Gaussians andthresholding.

FIG. 17 shows a flow chart of an example procedure for dehazing aretinal image via spectral analysis.

FIG. 18 shows a flow chart of an example procedure for performingautomatic montage image montage.

FIG. 19 shows a flow chart of an example procedure for enhancing retinalimage spectral dehazing by using camera alignment information computedfollowing Purkinje reflection position detection in order tocompute/retrieve estimated haze and transmission masks via a referenceoptical light scattering model.

FIG. 20 shows an illustrative example of wide field fundus camera havingthe illumination beam projectors optically coupled to the centralviewing axis using a beam splitter or mirror.

FIG. 21 shows an illustrative example of a montage where the wide fieldfundus camera is in a non-central alignment with respect to the eye.

FIG. 22 shows an illustrative example of a montage with assumed symmetryof retinal illumination and haze due to central alignment of the widefield camera with the central axis of the eye.

FIG. 23 shows an illustrative example of an algorithm that can be usedto dynamically generate montaging masks for asymmetrically illuminatedretinal images.

DETAILED DESCRIPTION

FIG. 1 shows the Retcam contained on a rolling cart with a handheldimaging camera 601. A computer on the cart connects to the camera sensorinside the handheld imaging camera. Halogen illumination on the cartconnects via fiber optic cable to the handpiece. B The contact lens 602of the handpiece is positioned on the neonate's cornea followingdilation and lid speculum placement C, D Fiber optic illumination 603 isrouted thru the lens module 604 to the front of the handpiece 605 at thesides of the imaging lens 606 to create ring illumination 611. ERepresentative field of the entire retina divided into zones I, II, andIII used for retinopathy of prematurity screening (ROP). Direct ringillumination may cover a 120-degree field of view allowing macularcentered pictures to reach zone II of the retina, but requiringrepositioning of the handpiece in up to 9 locations to fully image theentire peripheral retina in zone III to the Ora Serrata 607. F Ringillumination may create a “donut” in some patients 608, withillumination falling off peripherally and centrally. G Some peripheraldetails of the retina such as a demarcation line associated with ROP(609—white arrows) may be less visible if there is insufficientperipheral illumination of the retina. H In adult patients there may beprominence of the human lens reflection (Purkinje III and IV reflection)of the ring illumination, which occurs due to changes in the refractivepower of the human lens following the neonatal period 610.

FIG. 2 shows an illustrative example of a wide field fundus camera 100with multiple illumination beam projectors 30 a-30 n and a narrow beamprojector 40. The wide field fundus camera 100 includes primarily anobjective lens 10, an image recording device 20, a plurality ofillumination beam projectors 30 a-30 n, a narrow beam projector 40, afirst polarizer 13 and a set of second polarizers 31 a-31 n. The widefield fundus camera 100 further includes a contact lens 12, a focusinglens 17, an electronic controller 50 and an image display 60.

Objective lens 10 may be an aspherical lens and is located at a firstend of the wide field fundus camera 100. The objective lens 10 defines asymmetric viewing axis 11 and a working plane 6 of the wide field funduscamera 100. The plurality of illumination beams 32 a-32 n emergingthrough an illumination aperture 8 are pre-focused at the working plane6. When a subject eye 1 is aligned with the wide field fundus camera 100for fundus viewing, subject pupil 3 is about to position at the workingplane 6 and the illumination beams 32 a-32 n are projected into subjectpupil 3 to illuminate the subject retina 2 for alignment and forphotographing. At a proper alignment, objective lens 10 produces a firstretina image near its back focal plane 5, and the first retina image isthen re-imaged into the image recording device 20. The illuminationaperture 8 is located at the back focal plane 5 so as to defineillumination area on the subject retina 2.

At a proper alignment, objective lens 10 also forms an image of thesubject pupil 3 onto the plane of optical stop 14, which thus defines asmall, virtual viewing window on the subject pupil 3 for the camera 20to look through into the retina 2. The illumination beams 32 a-32 n arethus respectively focused at the subject pupil 3, and the focal spotsare pre-positioned outside the virtual viewing window. Therefore, anyscattering light of illumination beams 32 a-32 n scattered outside thisvirtual viewing window will be substantially blocked from getting intothe image recording device 20.

In an illustrative example, the wide field fundus camera 100 may providea static field of view of 120 degrees or wider on the subject retina 2.In this illustrative example, the objective lens 10 has an optical powerof about 120 D and a diameter of about 18 mm. The objective lens 10 hasthus a back focal length of shorter than 8 mm and a small workingdistance of approximate 4 millimeters with respect to the subject cornea7. The objective lens 10 may be an aspherical lens such that to haverelative lightweight and to produce optimal image quality over thesubject retina 2.

A contact lens 12 may be positioned in front of the aspherical objectivelens 10 and in direct contact with the subject cornea 7. The contactlens 12 may or may not have optical power. FIG. 2 shows how a contactlens 12 is incorporated with the aspherical objective lens 10 to producea first retinal image of the retina 2. In an illustrative example, thecontact lens has a diameter of about 10 mm to fit for the small eyeball1 of infants.

There are commercially available aspherical lenses for retinal viewing,with indirect ophthalmoscopes or slit lamp microscopes. For instance, anaspherical lens integrated with a contact lens can be found in an OcularORMR-2x (Ocular Instruments, Bellevue, Wash., United States of America).

The image recording device 20 is located at a second end of the widefield fundus camera 100 and is to view and to photograph fundus imagethrough objective lens 10. Also, this image recording device 20 is in anillustrative example able to perform auto-focusing and auto-exposurecontrol. The image recording device 20 in an illustrative example mayinclude a consumer image recording device that includes advancedfeatures of autofocus, auto exposure, real-time display, and imagestorage and transfer, and that is compact, lightweight, and easy to use.The image recording device 20 may have a built-in function to readilytransfer its recorded image to a local computer or another processor forinternet connectivity and telemedicine networks. The image recordingdevice 20 as an illustrative example may have a resolution over twomegapixels and have an entrance pupil of 8 mm or bigger to receive alllight passing through the optical stop 14. The image recording device 20may have a feature of a custom setting and be capable of saving workingparameters for convenient operation. The image recording device 20 mayhave a separate display 60 for easy viewing, to provide a desirableviewing angle, display size, and display distance.

The image recording device 20 in an illustrative example is a smart lenstype of consumer camera, such as a Sony QX100 (Sony Corporation, Japan).In this illustrative example, the image recording device 20 is coupledto the display 60 via Wi-Fi, and the display 60 may be a wireless devicesuch as an iPhone or an iPad. Also, this image recording device 20 mayhave high sensitivity and high-resolution operation.

The plurality of illumination beam projectors 30 a-30 n may include twoor more illumination beam projectors 30 a-30 n. Each of the projectors30 a-30 n projects an illumination beam 32 a-32 n at an angle toward theobjective lens 10. In an illustrative example, each illumination beam 32a-32 n has a small vergency and has a beam size to cover theillumination aperture 8. This way, each illumination beam 32 a-32 n isto mimic the illumination of an indirect ophthalmoscope and toilluminate a portion of an image on the subject retina 2. In anillustrative example, the plurality of illumination beam projectors 30a-30 n produces four illumination beams 32 a-32 n, of which eachilluminates a quadrant of the field of view on the subject retina 2.

A wide field fundus camera 100 may be operated in the mydriaticcondition, and white light illumination can be used for both aligningand photographing the subject retina 2. In an illustrative example, eachof the plurality of illumination beam projectors 30 a-30 n includes ahigh brightness, high power white LED and a projection lens to produce awhite light illumination beam 32 a-32 n. The white light LED may includea warm white light source with a color temperature about 3000 degreesKelvin. For radiation safety, each illumination beam 32 a-32 n islimited to project a few milli-watts of illumination power.

When another illumination condition is desirable, the illumination beamprojectors 30 a-30 n can include one or more of high power, highbrightness infrared LEDs. Further, the illumination beam projectors 30a-30 n can include one or more of high power, high brightness LEDscapable of projecting a limited spectral range of illumination such asred, green, or blue light.

The projection angle of the illumination beams 32 a-32 n may be set soas to move corneal and crystalline lens reflections away from thecentral viewing area. On the other hand, the projection angle of theillumination beams 32 a-32 n is limited to the minimum pupil size thatthe wide field fundus camera 100 is intended to use. For screening forROP, the minimum pupil size is set to approximately 5 mm, and theprojection angle of the illumination beams 32 a-32 n is thus set toabout 10 to 15 degrees.

The narrow beam projector 40 is to project a narrow illumination beam 42and to form a bright illumination feature on the retina 2 to facilitateauto focusing of the image recording device 20. Typically, a consumerimage recording device 20 requires a relatively high illumination leveland a relatively high contrast target feature to obtain reliable andeffective auto focusing. A bright and narrow slit beam illumination onor near the center of retina 2 is illustrated. In one illustratedexample, the dimensions of the slit beam are about 3 mm long and 1 mmwide on the retina 2.

The narrow illumination beam 42 is to project at an angle with respectto the viewing axis 11. In an illustrative example, the narrow slit beam42 is focused outside the virtual image window and has no overlap withthe image beam path throughout the crystalline lens 4.

The first polarizer 13 and the set of second polarizers 31 a-31 n mayform a cross-polarization condition to reject specular reflections ofthe illuminations beams 32 a-32 n back into the image recording device20. For a predetermined orientation of the first polarizer 13, each ofthe second polarizers 31 a-31 n may be rotationally adjusted to form aprecise condition of cross polarization. Specular reflections atsurfaces of the objective lens 10 and contact lens 12 are particularlystrong and necessary to remove. Specular reflections from the firstcorneal surface (i.e. first Purkinje reflection), the first surface ofthe crystalline lens (i.e., third Purkinje reflection) and the secondsurface of the crystalline lens (i.e., fourth Purkinje reflection) canbe a major source of image haze. A high extinction ratio of crosspolarization is required for reflection haze reduction. The polarizers31 a-31 n and 13 may be selectively thin film polarizers and have anextinction ratio of 300 or higher throughout the visible and infraredlight spectrum.

The contact lens 12 may serve as an optical window of the wide fieldfundus camera 100 to interface with the subject cornea 7. The contactlens 12 is illustrated to have an anti-reflection coating on its convexsurface. As the illumination beams, 32 a-32 n and the narrowillumination beam 42 are small and bright on the contact lens 12, effortis required to minimize and to remove specular reflection from itsconvex surface that interfaces to air.

The focusing lens 17 in one illustrative example is an achromatic lenswith a focal length about 60 mm to 80 mm and is positioned one focallength away from the back focal plane 5 of the objective lens 10. In oneillustrative example, the collimation lens 17 is to reimage the firstretinal image formed by the objective lens 10 into distance, and thusthe image recording device 20 is operated to focus at distance. Thisway, the focal length of camera 20 can be adjusted continuously to matcha desirable field of view, and the selected retinal image area can thusfill up the camera display 60. As a result, the pixel resolution of thecamera and its display can be optimized. Focusing lens 17 and objectivelens 10 may form an optical afocal relay, to relay the outgoing beamfrom the subject pupil 3 to the image recording device 20. The opticalafocal relay has a scaling factor m, equal to the ratio of the focallengths between the focusing lens 17 and the objective lens 10. In anillustrative example, the focusing lens 17 has a focal length of 60 mm,and the optical afocal relay has a scaling factor m of about 7.5.

Optical stop 14 may be positioned in front of the image recording device20 and is conjugated with the working plane 6 of the wide field funduscamera 100 via objective lens 10. The optical stop 14 has an aperturecorresponding to a predetermined virtual viewing window on the subjectpupil 3. For instance, for a scaling factor of 7.5 and a virtual viewingwindow of 1.3 mm on the subject pupil 3, the optical stop 14 is thus 10mm. In operation, the subject pupil 3 is aligned with the working plane6, and the optical stop 14 blocks any light scattered from outside thevirtual viewing window on the subject pupil 3. The aperture of theoptical stop 14 may also be limited to the effective aperture of theimage recording device 20.

The electronic controller 50 is to couple with the image recordingdevice 20 and to power the illumination projectors 30 a-30 n and thenarrow beam projector 40. In an illustrative example, the electroniccontroller 50 powers the illumination projectors 30 a-30 n at a lowpower level during alignment and then ramps up them to a high powerlevel for photographing the subject retina 2. The power level of each ofthe illumination projectors 30 a-30 n can be controlled in aprogrammable manner. This way, the illumination projectors 30 a-30 n canbe synchronized with the image recording device 20 to take multipleretinal images with various on-off configurations and time sequences.

The display 60 may couple with and display real-time images of the imagerecording device 20. In an illustrative example, the display 60 is ahigh definition monitor and is coupled wirelessly to the image recordingdevice 20. For instance, the image recording device 20 may be a SonyQX100 (Sony Corporation, Japan) and the display may be an iPad (Apple,Cupertino, Calif., United States of America) and data transfer betweenthe two devices may be through Wi-Fi built into the devices.

The images captured by the image recording device 20 may be stored inthe camera 20, monitored at the display 60, and transferred to a localcomputer or other networked computers. The images captured by the imagerecording device 20 may thus be viewed through the network, and retinaldiseases can be diagnosed by a retinal professional in a local or remotelocation.

A digital controller 50 may be used to independently control eachillumination beam projector 30 a-30 n. In an illustrative example, thereare four independent LED beam projectors controlled by a digitalcontroller. The controller may be connected to a tablet through its USBport, and the user interface to the image recording device 20 and thedigital controller 50 may be provided on the tablet display.

In FIG. 8, an illustrative example demonstrates how the user can controleach of the four independent beam projectors 30 a-30 n and turn each oneon or off via an illumination pattern selector 804. The independent beamprojectors 30 a-30 n may also be serially programmable, and the pattern,timing, and beam illumination intensity can be controlled by the uservia an illumination mode selector 805. The power level for eachindependent beam projector 30 a-30 n may be controlled for bothreal-time live-view imaging of the retina, as well as flash photographyvia an illumination level adjustor 806. For flash photography, theillumination beam projectors 30 a-30 n may be temporarily adjusted to ahigher intensity than in live-view imaging mode, for the purpose offinal photo acquisition or auto-focusing purposes. Rapid sequentialserial illumination control of each independent beam projector 30 a-30 nmay allow the retinal view provided by each independent beam projectorto be shown simultaneously in separate live-view images of the retina800, 801, 802, 803. For example one of four independent illuminationbeam projectors 30 a-30 n can be individually turned on and the retinalimage resulting from each of four independent beams then shown in fourseparate panels on the same display 800, 801, 802, 803. In anillustrative example, each independent beam projector 30 a-30 n may beturned on for less than 100 ms, serially turning on each beam projector30 a-30 n one at a time, allowing acquisition of the views provided byeach of the four independent beam projectors in less than 400 ms. Thistiming can prevent lag in the live-view and allow the user to align thecamera with the eye to optimize illumination provided by eachindependent beam projector 30 a-30 n.

In a separately illustrated example in FIG. 10, a single live view imageof the retina may be provided, and each independent beam projector 30a-30 n can be turned on and then off for a discrete period of time. Saidbeam projectors turn on rotating clockwise or in another programmedmanner, one or more projector beams at a time, to allow the user to seethe illumination provided by each beam projector for assessing alignmentof the camera with the eye prior to final retinal image acquisition. Forexample, one of four independent beam projectors 30 a-30 n may be turnedon for 250 ms 1000 and then turned off. Then the next independent beamprojector is turned 1001 on for 250 ms and then turned off. Then thenext independent beam projector is turned 1002 on for 250 ms and thenturned off. Then the next independent beam projector is turned 1003 onfor 250 ms. This sequence of beam illumination control could be repeateduntil a final retinal image is acquired. The four panels shown in FIG.10 1000, 1001, 1002, 1003 provide an example display seen at fourdifferent points in time and would appear to the user as a rotating beamin real-time. Each independent beam projector 30 a-30 n may create aclear quadrant of viewing of the retina 1000, 1001, 1002, 1003 as wellas an area of lens haze and reflections 1004, 1005, 1006, 1007 due toscattering of the illumination beam in objective lens 10, and the humanlens 4.

A method may be used to process the multiple retinal images provided byeach independent projector beam 30 a-30 n and to stitch them into asingle fundus image. An illustrative example of this method is aprocessor circuit coupled to a memory circuit, the memory circuitincluding instructions that cause the processor circuit to receiveimaging information corresponding to the plurality of retinal images andto provide a composite image including stitching together the pluralityof retinal images into a single montage image. Please refer to FIG. 9.In an illustrative example, a plurality of retinal images is acquiredfor four independent beam projector 30 a-30 n, turned on sequentiallyone at a time with the separate acquired retinal images shows as 900,901, 902, and 903. Image haze from the specular reflections from thehuman lens is evident in each image and is indicated by 906, 907, 908,and 909. The portion of each image without human lens haze 900, 901,902, 903 using said method can be stitched together to form a finalmontage image 905. Blending may be performed on the separate images thatform the final montage to eliminate seams and even exposure across thefinal montage. The method used to process said multiple retinal imagesmay also identify the human lens haze (906, 907, 908, 909), forillustrative example by both its contrast level and characteristicposition based on which independent illumination projection beam is onand the angle the projection beam has with the eye. This haze may bemasked by said image processing method before performing the finalmontage.

FIG. 3 shows an illustrative example of a wide field fundus camera 200having an illumination beam projector 230 n turned on for taking one ofthe multiple retinal images. The illumination beam projector 230 nprojects an illumination beam 232 n onto the objective lens 10 at anangle with respect to the viewing axis 11, mimicking the illuminationconfiguration of an indirect ophthalmoscope. The illumination beam 232 nis then focused on the working plane 6 and directed into subject pupil3. This illumination beam 232 n passes through the subject pupil 3 andturns into illumination beam 233 n to illuminate subject retina 2.

Because the illumination beam 232 n is projected at an angle and isshaped by the apertures 8 and 9, the illumination beam 232 n can thus befocused into subject pupil 3 and be away from the pupil center. In anillustrated condition, the illumination beam path is not overlapped withthe image beam path inside the crystalline lens 4, and scattering lightscattered from the crystalline lens 4 is not captured by the imagerecording device 20. In this way, image haze resulting from lensscattering of the illumination beam inside a less-transparentcrystalline lens may be significantly reduced.

Also, because the illumination beam 232 n is projected at an angle andis shaped by the apertures 8 and 9, the illumination beam 233 n is notsymmetric on the subject retina 2. More than a quadrant of the field ofview may be illuminated via such an illumination configuration. At thisillumination condition, an image captured by the image recording device20 may show only a portion but not the full field of view beingilluminated. Therefore, multiple images may be required to capture thesubject retina 2 to have a full field of view. In an illustrativeexample, four illumination beam projectors 230 are used and four retinalimages may be captured in time sequence to provide a 120-degree field ofview of the subject retina 2.

FIG. 3B shows an illustrative example of an ultra-wide field funduscamera 200B modified from FIG. 3. A meniscus lens 12′ is inserted inbetween the contact lens 12 and the objective lens 10 to form anultra-wide field objective lens including the contact lens 12, themeniscus lens 12′ and the objective lens 10. Preferably, the contactlens 12 is formed with a plastic contact element of low diopter power,and the meniscus lens 12′ is a glass lens of much higher diopter power.The objective lens 10 can be an aspherical lens and can be aspherical onboth front and back surfaces to correct optical aberrations for theultra wide field of view.

In a preferable symmetric configuration of the illumination beams, 4 or8 illumination beam projectors 230 are used to provide axial symmetricillumination with respect to the instrument axis 11. In a preferableoperation procedure, two or four illumination beams 232 a-232 n can beused to produce central symmetric illumination beams 233 a-233 n on theretina when the instrument axis 11 is aligned with the eye optical axis.Once such an on-axis alignment is achieved, the reflection spots fromthe contact lens surfaces and the ocular surfaces and the scatteringhaze from the cornea 7 and crystalline lens 4 are distributedsymmetrically on the retinal image (e.g. photo image 1100 a).Consequently, the reflection spots and scattering haze can be used toguide the centration and axial alignment of the fundus camera 200Btoward a symmetric distribution with respect to the image center.

FIG. 4 shows an illustrative example of a wide field fundus camera 300having the narrow beam projector 340 turned on to facilitateautofocusing through less transparent crystalline lens 4 and reflectionhaze. The narrow beam projector 340 is to project a narrow illuminationbeam 342 and to form a bright illumination feature on the subject retina2. A consumer image recording device 20 may require a relatively highillumination level and a relatively high contrast target feature toobtain reliable and effective auto focusing. In particular, a bright andnarrow slit beam illumination on or near the center of the subjectretina 2 may be favorable for such autofocusing. In one illustratedexample, the dimensions of the slit beam are about 3 mm long and 1 mmwide on the subject retina 2.

The narrow slit beam 342 can be projected at an angle with respect tothe viewing axis 11. In an illustrative example, the narrow slit beam342 is focused outside the virtual image window and has no overlap withthe image beam path throughout the crystalline lens 4. This way the slitbeam image on the image recording device 20 is not blurred by scatteringlight from the crystalline lens 4, and the narrow slit beam 342 thusserves to facilitate autofocusing through less transparent crystallinelens 4.

FIG. 5 shows one illustrative example of a wide field fundus camera 400having one slit beam projector 430 n turned on to improve image takingthrough less transparent crystalline lens 4 and reflection haze. Theslit beam projector 430 n projects a slit beam 432 n toward theobjective lens 10, in which the slit beam 432 n has a narrow dimensionin the incident plane of the illumination and a full dimension normal tothe incident plane. As shown in FIG. 5, such a slit beam 432 n turnsinto a slit illumination beam 433 n on the subject retina 2. Also, sucha slit beam 432 n is confined away from the viewing axis 11 and thus mayhave a better clearance with the image beam path inside the crystallinelens 4. Consequently, an overlapping region between the illuminationbeam path and the image beam path can be avoided inside the crystallinelens 4, and thus image haze due to light scattering inside lesstransparent crystalline lens 4 may be substantially improved.

In an illustrative example, the slit beam 432 n of FIG. 5 may provide aretinal slit image of approximately 60 degrees in the narrow dimensionand 120 degrees in the length dimension, i.e., a dimension normal to theincident plane of the page. In one illustrative example if such aretinal slit image is taken at a rotational angle of 60 degrees separatefrom each other, then three of such retinal slit images may cover thefull image of the subject retina 2. In an illustrative example, threeslit beam projectors 430 a-430 n are positioned 120 degrees from eachother around the symmetric viewing axis 11, and each projects a slitbeam 432 n with its narrow dimension orientated in its own incidentplane. In this case, three retinal images may be taken to form acomplete full field of view of the subject retina 2. Similarly, inanother illustrative example if the slit beam narrow dimension is about40 degrees, five of slit beam projectors 430 a-430 n may be used, andfive slit beam images may be taken to cover a full field of view of thesubject retina 2 with the objective lens 10.

FIG. 6 shows an illustrative example of a handpiece 500 that integratesa central housing 570 for the multiple illumination projectors, a fronthousing 571 for the objective lens, an image recording device 520 and acontact lens 512 of the wide field fundus camera. In this illustratedexample, the image recording device 520 is a Sony QX100, and it isaffixed to the central housing 570 via a mechanical coupler 560. Thecontact lens 512 may be mounted on a contact lens holder 572, which isattached to the front housing 571. This way the contact lens 512 may beremoved with the holder 572 for easy sterilization.

In one illustrative example, the handpiece 500 may have an elongatedshape, having dimensions about 60 mm in diameter and 200 mm long. Inanother illustrative example, for screening for ROP, the front end ofthe handpiece 500 is about 10 mm in diameter.

FIG. 7 shows an illustrative example of a handpiece 500 that integratesa central housing 570 for the multiple illumination projectors, a fronthousing 571 for the objective lens, an image recording device 520 and acontact lens 512 of the wide field fundus camera. In this illustratedexample, the image recording device 520 is an Olympus Air A01 (OlympusCorporation, Japan) and it is affixed to the central housing 570 via amechanical coupler 560. In one illustrative example, images from theimage recording device 520 may transmit via Wi-Fi to a tablet displaywhich in this illustrated example is a Samsung Galaxy Note 501

FIG. 8 shows the tablet display for one illustrated example of theelectronic controller. In this example, four independent illuminationbeam projectors are controlled by the electronic controller. Theelectronic controller serially may turn on each illumination beamprojector one at a time, and the image recording device 520 may capturean image with each illumination beam. 801 shows the first illuminationprojector beam turned on with all other beams turned off, 802 shows thesecond illumination projector beam turned on with all other beams turnedoff, 803 shows the third illumination projector beam turned on with allother beams turned off, 800 shows the fourth illumination projector beamturned on with all other beams turned off. For example, the total timeto turn on and off each of the four independent beams may be less than400 milliseconds, with 100 milliseconds for each beam. Said process mayallow a real-time display of how the retinal image formed by eachindependent beam will appear to assess alignment of each independentbeam projector with the eye. The pattern of serial illumination controlof each independent beam projector may be controlled by the user and maybe programmable by selecting one of four possible patterns 804. Eachindependent beam projector may be manually and independently turned onand off through a separate user control 805. Power levels for eachindependent illumination projection beam may be controlled by the userboth for real-time live examination and flash photography level when thefinal photo is captured by the image recording device 806.

FIG. 9 shows one possible illustrated example for a method of imagestitching of the plurality of images taken by independent illuminationprojector beams. In this example, four retinal images are taken, eachhaving one of four independent beam projectors turned on. 901 shows thefirst illumination projector beam turned on with all other beams turnedoff, 902 shows the second illumination projector beam turned on with allother beams turned off, 903 shows the third illumination projector beamturned on with all other beams turned off, 900 shows the fourthillumination projector beam turned on with all other beams turned off.Each independent beam projector may create a specular white reflectionand haze 906, 907, 908, 909, from the human lens of the eye 4 and theobjective lens 10, but also illuminates a quadrant of the retina withoutlens haze 900, 901, 902, 903. The image processing method may remove thearea in each illumination projector beam image where there is lens hazefrom the human lens 906, 907, 908, 909, and join the portion of eachillumination projector beam image without lens haze 900, 901, 902, 903.Blending may be performed on the stitched pieces to seamlessly blenddifferences in exposure level of each illumination projector beam image.The final montage 905 may eliminate the lens haze 906, 907, 908, 909from the montaged image. The image processing method may include aprocessor circuit coupled to a memory circuit, the memory circuitincluding instructions that cause the processor circuit to receiveimaging information corresponding to the plurality of retinal images andto provide a composite image including stitching together the pluralityof retinal images into a single montage image. It may further include aprocessor circuit coupled to a memory circuit, the memory circuitincluding instructions that cause the processor circuit to receiveimaging information corresponding to the plurality of retinal images andremove artificial reflection spots and lens haze from each of saidplurality of retinal images.

FIG. 11 shows an illustrative example of an ultra-wide FOV image of ababy eye 1100 a taken with a wide-field fundus camera using anultra-wide FOV lens according to FIG. 3B. FIG. 11a shows fourillumination beam projectors 230 n, 230 a positioned at 12, 3, 6, and 9o'clock about the central viewing axis 11 that illuminate the retina 2to provide an ultra-wide FOV image of the retina 1100 a. The ultra-wideFOV image of the retina 1100 a is processed using an illustrativeexample of a real-time dehazing algorithm to generate a dehazedultra-wide FOV image of the retina 1100 b. Four illumination beams 230n, 230 a are used and four reflection spot clusters 1102-1105 aresymmetric with respect to the center of the retinal image 1101 a. Thereflection haze pattern is also substantially symmetric with respect tothe center of the retinal image 1101 a. Each reflection spot cluster mayinclude visibly two or more reflection spots 1102 a from the contactlens 12, the cornea 7 (Purkinje I and II) and the crystalline lens 4(Purkinje III and IV) and scattering haze spot from the corneal tissueand lens 1106 a. In an alignment shown in photo image 1100 a, the fourreflection spot clusters 1102-1105 are located at 12, 3, 6, and 9o'clock positions, because the four illumination beam projectors areorientated at x and y positions with respect to the instrument axis 11of wide field fundus camera 200B. During an alignment process, thelocations and movements of these reflection spots can be used asindicators to guide instrument alignment to obtain alignment of thewide-field fundus camera FIG. 3B, with the central axis of the eye 11.

FIG. 11b shows the same photo image 1100 b as shown in 1100 a, followingfurther processing of said photo image 1100 a using an illustrativeexample of real-time dehazing to generate a dehazed image 1100 b.Comparing to photo image 1100 a, photo image 1100 b demonstrates moreretinal details to enable better judgment on alignment of wide fieldfundus camera 200B and focus of retina 2 on wide field fundus camerasensor 20.

Real-time dehazing is a computer function implemented in a processorcircuit associated with the fundus camera 200B of FIG. 3B to reduceimage haze in a real-time manner, generating a dehazed image in oneillustrative example in less than 200 milliseconds. The processorcircuit can be a high-speed computing processor, e.g. a high-speedlaptop computer. The computing processor is coupled with the camera toenable real-time image processing and display. Real-time dehazing can beaccomplished in one illustrative example by computing the estimated hazemap using at least one of reference spectrum and size and spatialdistribution of said reflected and scattering haze, computing thetransmission map utilizing estimated haze map for said wide field fundusimage, refining the transmission map utilizing estimated retinaltransmission from a reference retinal wide field fundus image, toproduce a dehazed retinal image.

In one illustrative example, selection of elements comprising an ultrawide-field fundus camera lens (10, 12′, 12) and design of illuminationbeam projectors 230 n, 230 a, allows simultaneous visualization ofPurkinje reflections 1102 a-1105 a and retinal image (ie optic nerve1107 a) details. In this illustrative example, this is enabled byprojection angle of 12 degrees for said illumination beam projectors,use of a 160-degree field of view ultra-wide field lens, with asphericalcurvature and field of view sufficient to visualize said Purkinjereflections within the FOV, and wide field fundus camera lens 20 withdepth of field sufficient for simultaneous visualization of Purkinjereflections and retina within said ultra-wide FOV image. Purkinjereflections 1102 a-1105 a and retinal image (ie optic nerve 1107 a)details can be used to guide alignment of said wide field fundus camera200B with the retina 2. Real-time dehazing of the wide field fundusimage can reveal additional retinal details 1106 b, enhance appearanceof retinal structures such as the optic nerve 1107 b, and enhanceappearance of the Purkinje reflections 1102 b-1105 b to facilitatealignment of the wide field fundus camera 200B with the retina 2.

FIG. 12 shows an illustrative example of two sequential photo images1200 a and 1200 b captured by the ultra-wide field fundus camera 200B ofa baby eye. FIG. 12a shows a retinal image 1200 a captured by said widefield fundus camera 200B using two illumination beam projectors 230 npositioned at 3 and 9 o'clock around the central viewing axis 11. FIG.12b shows a retinal image 1200 b captured by said wide field funduscamera 200B using two illumination beam projectors 230 n positioned at12 and 6 o'clock around the central viewing axis 11.

In photo image 1200 a, the reflection spot clusters 1203 a and 1205 aare aligned horizontally to center with retinal image 1201 a, and thereflection haze pattern is substantially symmetric with the imagecenter. In photo image 1200 b, the reflection spot clusters 1202 b and1204 b are aligned vertically to center with retinal image 1201 b andthe reflection haze pattern is substantially symmetric with the imagecenter.

The symmetric haze pattern 1206 a and symmetric reflection spot clusters1203 a, 1205 a, 1202 b, 1204 b, along with the position of retinaldetails such as the optic nerve 1207 a in the field of view, provide avisual judgment for the alignment of the wide field fundus camera 200Bwith the retina 2. Misalignment of the camera with respect to thecentral visual axis of the eye as measured by alignment errors in x, y,and z axis as well as tilt can be computed using the position of thesereflection spot clusters 1203 a, 1205 a, 1202 b, 1204 b as well as theposition of retinal details such as the optic nerve 1207 a in the widefield retinal image 1200 a, 1200 b. With correct alignment of the widefield fundus camera 200B with the central axis of the eye the presenceof standardized symmetric haze patterns 1200 a and symmetric reflectionspot clusters 1203 a, 1205 a, 1202 b, 1204 b enable efficient removal ofthe image haze using standardized digital masks.

The sequential photo images 1200 a and 1200 b are taken with electroniccontroller 50 of FIG. 2. The sequential photo images 1200 a and 1200 bare in one illustrative example preferably taken within a fraction of asecond to avoid eye movement. In another preferred embodiment,sequential photo images are taken as four or more sectional images eachsectional image with one pair of axially symmetric (e.g 1203 a, 1205 a)illumination beams generated by illumination beam projectors 230 n toilluminate the retina. In a further preferred embodiment, sequentialphoto images are taken with with illumination beam projectors 230 nwhere said illumination beams are slit beams.

FIG. 13a shows an illustrative automated montage image 1300 a generatedwith real-time dehazing and auto-montage from the two sectional retinalimages 1200 a and 1200 b of FIG. 12, and FIG. 13b shows a final montageimage 1301 b with further image enhancement as compared to theauto-montage image 1301 a. As a result, a single montage 1301 b isobtainable with a full ultra-wide FOV using the ultra-wide field lens(e.g. a combination of contact lens 12, inserted meniscus lens 12′ andaspherical lens 10 of FIG. 3B) on the wide field camera 200B.

To obtain the automated montage image 1301 a, real-time dehazing isperformed on the sectional retinal images 1200 a and 1200 b, consistingof generation of an estimated haze map, digital masking of stereotypicalhaze and Purkinje reflection in said sectional retinal images, removalof additional haze from said masked sectional images by refining thetransmission map using a reference haze free wide-field retinal imageand dehazing of the masked sectional images using said transmission map.Dehazed masked sectional images are then montaged using the automatedmontage algorithm by aligning the sectional images using automaticallygenerated control points, and then blending areas of overlap of saiddehazed masked sectional images. This produces a seamless full FOVmontage image 1300 a that has decreased haze and removal of Purkinjereflections as compared to the component sectional images 1200 a and1200 b.

To obtain a final montage 1301 b, a further dehazing is performed on theinitial montage 1301 a to remove residual haze and to enhance retinalimage contrast. In a preferable embodiment, the instruction for adehazing algorithm are computing processor-accessible and when executedfurther remove residual haze from the montage image 1301 a and to createa haze-free montage image 1301 b.

Instant auto-montage and haze-free image are highly desirable featuresof the ultra-wide field fundus camera 200B of FIG. 3B. It has beendemonstrated that sequential photo images with horizontal spots 1200 aand vertical spots 1200 b can be taken within a fraction of a second toavoid eye movement and to simplify auto-montage process for instantauto-montage (e.g. in less 400 milliseconds). It has also beendemonstrated that a dehazing algorithm can further remove residual hazefrom the montage 1301 a and to create a haze-free full FOV montage image1301 b digitally and automatically.

Such an ultra-wide FOV image of 1301 b is thus taken at a singlealignment position. Such a single alignment montage can thus be obtainedvia a standardized alignment procedure using said Purkinje reflections1203 a 1201 a 1202 b 1204 b and visualization of said retinal structuressuch as the optic nerve 1107 a, and a simplified auto-montage algorithmbased on wide field fundus camera alignment with the central axis of theeye. As a result, such a single alignment 180-degree ultra-wide fieldmontage can be taken within one sequential image acquisition so as tosignificantly reduce the number of image acquisitions needed to fullyimage the retina edge to edge

FIG. 14a shows an illustrated example of a sectional retinal image priorto processing with the dehaze algorithm. In a preferred embodiment theimage of 14 a is processed according to a dehaze algorithm described inthe flowchart for FIG. 17, generating an estimated haze map using thespectral characteristics of haze created by illumination beamprojectors. In the example process of a preferred embodiment of thedehaze algorithm, the blue channel (FIG. 14a ) is used as an estimatedhaze mask, which is made possible by spectral reflections from theretina primarily composed of red and green light. A blur process is usedon the haze mask generated from the blue channel (FIG. 14c ) to removehigh frequency information that may contain retinal detail (so that thedetail is not further masked out by the following steps in the dehazealgorithm). The brightest pixel in the blurred blue channel is selectedand used to create a bias mask (FIG. 14d ) by creating a greyscale RGBmask with all channel values equal to the brightest value in the blurredblue channel (FIG. 14c ). Dividing the blurred blue channel by this biasnormalizes the haze map. This map is then scaled down and inverted inorder to produce a transmission mask (FIG. 14e ) in which each pixelvalue is proportional to the signal-to-noise ratio of the correspondingpixel in the original input image. To apply this transmission mask tothe source image, first the bias mask is subtracted from the inputimage, and then that difference is divided by the transmission mask.Finally, the bias mask is added back again to that quotient, anynegative values in the resulting image are replaced with their absolutevalue, and then the image is clamped so that all no color is darker thanpure black or brighter than pure white. The resultant dehazed image FIG.14f improves the clarity of retinal details by removing reflected andscattered haze from the original wide field retinal image FIG. 14 a.

The rationale behind the creation of the bias mask stems from anassumption that haze in the image is being produced by a diffuse ambientwhite light source. If the blue channel is taken to estimate the hazemask, then the brightest value in the blue channel can be taken as anestimate of the brightness of the ambient light source generating thehaze. Furthermore, if a pixel position has a low transmission value(close to zero), then any channel value in the input image'scorresponding pixel will become attenuated if its value is close to thebias value, and any channel value that is not close to the bias will besignificantly scaled up (as a result of subtracting the bias and thendividing by the transmission value). This causes channel values that arelikely the reflection of ambient light to be less emphasized, andchannel values that are likely to carry information to be moreemphasized.

FIG. 15a shows an illustrative example of a sectional retinal imagedemonstrating stereotypical illumination resulting from a single beamilluminator with the camera at a near-central alignment. 1500 a marks awell-exposed region of the retina, 1501 a marks a spot shrouded indiffuse haze, 1502 a is in the midst of a P1 Purkinje reflection, and1503 a is located on the border separating a well-exposed portion of theretina from the region shrouded in diffuse haze. Knowledge of whichillumination beam projectors are illuminated allows the resulting hazepattern on the retina to be estimated by simple reference to thestereotypical haze pattern shown in FIG. 15a for the given wide-fieldlens and given wide-field FOV. This pattern can additionally in anotherillustrative example be characterized by the blue channel component ofthe sectional retinal image as shown in FIG. 15 b.

FIG. 15c demonstrates an illustrative example using image thresholdingof the image in FIG. 15a to automatically identify the Purkinje P1reflection 1502 c. In an alternate embodiment, the Purkinje reflectioncan be identified by shape and by spectral frequency in the wide-fieldFOV image. Purkinje reflections will move within the wide field FOVdependent on camera alignment with the central visual axis. Automateddetection of the purkinje reflection allows calculation the centrationof alignment of the wide-field fundus camera with the eye. Knowledge ofwide field fundus camera alignment with the eye can inform dehaze andauto montage algorithms to enhance removal of reflected and scatteringhaze from wide-field retinal images and perform automated montage ofsectional images having improved clarity of retinal details.

FIG. 16a shows an illustrative example of a wide-field FOV retinal imagetaken at central alignment with 4 beam illuminators. 1600 a marks theoptic nerve, 1601 a marks the topmost purkinje P1 reflection, and 1602 amarks the topmost purkinje P4 reflection.

FIG. 16b shows an illustrative example of a wide-field FOV retinal imagetaken at a skewed alignment with 4 beam illuminators. It shows the sameretina seen in FIG. 16a . The nerve at 1600 b has much less detail dueto the misalignment, although its position within the wide-field FOVdoes not appear to have changed much to the naked eye relative to 1600a. The obvious change is seen at 1602 b where the topmost purkinje P4reflection 1602 b has moved a large distance away from the topmostpurkinje P1 reflection 1601 b. The purkinje P4 reflection 1602 b hashigh contrast with the retina and is easily detected automatically, asshown in FIG. 16c at 1602 c.

FIG. 16c shows an illustrative example of automated purkinje P4detection at 1602 c. In this illustrative example thresholding is usedto eliminate all but the Purkinje reflections, and difference ofGaussians is used to further differentiate the purkinje P4 reflection1602 b form the purkinje P1 reflections 1601 b. A vector can be computedthat originates at 1601 b and extends to 1602 c because the P1reflection at 1601 b is static and can be stereotyped for variousoptical configurations. Such a vector can be used to compute a magnitudeand direction of camera tilt misalignment with the retina. If more thanone such vector as used by detecting more than one pair of purkinje P1and P4 reflections, then it is possible to compute the rotation angle ofmisalignment.

Computing camera alignment makes it feasible to stereotype and modelreflection and haze patterns at various alignments, as opposed to onlyfor a central view shown in FIG. 15. This creates the opportunity toaugment the spectral dehazing process described in FIG. 14. The bluechannel haze mask can be refined by an estimated haze mask produced byan optical model that operates by considering the illuminator patternand the automatically-detected camera alignment.

FIG. 17 shows an illustrative example of a spectral dehaze algorithm. Itworks as described in earlier descriptions of FIG. 14.

FIG. 18 shows an illustrative example of an algorithm that seamlesslymontages a set of sequential retinal images taken in a centralalignment. The flow chart represents multiple sequences of eventshappening in parallel by the time bar at 1807. All event boxes in thechart that are located on the same horizontal line (and thus the same tvalue) occur simultaneously. This is only critical for the image capturesequence preceding the montage algorithm that spans t values of 1, 2,and 3.

The sequential sectional images in this process are taken at high-speedwith a set pattern of flashing illumination beam projectors. The cameraencodes the sequential order of each image inside the image acquisitionparameters located in the image file data. Step 1800 reads this datafrom each image to determine the image's sequence number, which is usedto generate a static blending mask (1801) that is stereotyped based onthe expected illumination beam projector flash pattern. At 1802, thismask is used to isolate the well-exposed region of each image. Eachimage is spectrally dehazed in 1803, and in 1804 isillumination-corrected via histogram and luminance analysis. 1804ensures that each region will have the same final light exposure beforebeing blending together, so that the four source regions can be easilyidentified in the final image. Finally at 1805, each image is blended atthe seams. Final image enhancement occurs at 1806, taking advantage ofglobal statistics available by having the entire FOV in a single image.This produces the final statically-montaged image.

FIG. 19 shows an illustrative example of an algorithm that uses anoptical model and computed camera alignment information to produceestimated haze and transmission masks that are used to refine a separateset of haze and transmission masks generated by a spectral dehazealgorithm such as the one exemplified in FIG. 14 and FIG. 17. At 1900,the algorithm receives the camera image from which it reads the imageacquisition parameters to know the illumination beam projector patternthat was flashed at acquisition time. This is used to select astereotyped set of expected purkinje P1 locations. Purkinje P4reflections are identified at 1901 by an algorithm such as the onedemonstrated in 1602 c. Then their positions are compared to thestereotyped purkinje P1 positions in order to derive camera positioninformation, such as by a process described in the details of FIG. 16.With alignment information and illuminator information known, a firstset of estimated haze and transmission masks are calculated at 1903using the optical model, and then at 1904 spectral analysis on the inputimage is used to generate a second set of haze and transmission masks.There are many possible embodiments to implement 1905 to obtainalternate refined haze masks. One possible embodiment is to compute thepointwise minimum of the two sets of masks. This will underestimate theamount of haze present, resulting in a more moderate effect on the finalimage but with the lowest chance of losing retinal image detail. Analternate embodiment is to average the masks, so that the resulting hazemask matches both input masks at pixels where they agree, and produces amiddle-ground estimate for pixels where they disagree. At 1906, themasks are applied to the image to produce the final dehazed imageoutput.

FIG. 20 shows an illustrative example of a wide field fundus camera 2000having an illumination beam projector 2030 n turned on for taking one ofthe multiple sectional retinal images. The illumination beam projector2030 n and 2030 a in a preferred embodiment are optically coupled to thecentral viewing axis 11 using a beam-splitter or mirror 2040. Theillumination beam projector 2030 n and 2030 a in an alternate embodimentmay be optically coupled to a plurality of mirrors or beamsplitters todirect light from the projectors along the central viewing axis 11. Theillumination beam 2032 n projected from the illumination beam projector2030 n is focused on the working plane 6. The illumination beam 2032 nthen passes through the subject pupil 3 and turns into illumination beam2033 n to illuminate the subject retina 2.

The illumination beam 2032 can be projected at an angle with respect tothe central viewing axis 11. In an illustrated example, the illuminationbeam path does not overlap with the image beam path throughout thecrystalline lens 4. In this way, image recording device 20 does notcapture the light scattered from the crystalline lens 4. Consequently,the image noise from the scattering light may be significantly reduced.

FIG. 21 shows an illustrative example of a montage where the wide fieldfundus camera is in a non-central alignment with respect to the eye.Using computed alignment of the wide field fundus camera with respect tothe eye, asymmetries in the reflected and scattered haze as well asretinal illumination can be adjusted for. Images FIGS. 21b, 21d and 21fillustrates how the dynamic mask might manifest for retinal images FIGS.21a, 21c and 21e respectively. The black areas 2101, 2103 and 2105 wouldbe regions to exclude whereas white regions 2102, 2104 and 2106 would bethe regions to include in the montage. As a result, a single montageFIG. 21g can be obtained with a full FOV defined with the ultra-widefield lens while substantially reducing the noise of the image.

FIG. 22 shows an illustrative example of a montage with assumed symmetryof retinal illumination and haze due to central alignment of the widefield camera with the central axis of the eye. Consequently, a staticmask may be used to exclude the symmetrical retinal haze in favor of thesectional images FIGS. 22a and 22b . When montaged, the results mayresemble the final image FIG. 22e with a full FOV defined with theultra-wide field lens.

FIG. 23 shows an illustrative example of an algorithm that can be usedto generate dynamic montaging masks for montaging asymmetricallyilluminated retinal images. It contains all of the steps of the enhanceddehaze algorithm described in FIG. 19 because the refined haze andtransmission maps that are generated from that process are useful fordeciding where to source pixel values at various pixel locations in theoutput image. The dynamic montage algorithm applies the enhanced dehazeprocessing steps in order to generate haze masks for each input image.Those masks are then used to score the visibility of each pixel in eachsource image. Finally, each pixel in the output image obtains its valuefrom the corresponding pixel in one of the source images by choosing thecorresponding pixel having the highest visibility score among all of thesource images.

The above-detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein. In the event of inconsistent usages between this document andany documents so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

As defined herein a “computer readable storage medium” is defined as atangible device that can retain and store instructions for use by aninstruction execution device. The computer readable storage medium maybe, for example, an electronic storage device, a magnetic storagedevice, an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that suchembodiments can be combined with each other in various combinations orpermutations. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1-37. (canceled)
 38. A wide field fundus camera, comprising: an objective lens having a viewing axis and disposed to form a retinal image; an image recording device disposed to capture said retinal image of said wide field of view; a plurality of illumination beam projectors positioned around said viewing axis and each configured to project an illumination beam at an angle toward said objective lens; a mechanism of cross polarization configured between said image recording device and said plurality of illumination beam projectors to reject specular reflections of said illumination beams; an image display operatively coupled to the image recording device to display said retinal image from said image recording device; an electronic controller operatively coupled to said plurality of illumination beam projectors to provide power to each of the plurality of illumination beam projectors in a predetermined sequence to provide illumination to obtain each of a plurality of retinal images; a real-time dehazing algorithm implemented to perform real-time removal of reflection and scattered light haze; a digital masking algorithm implemented to mask out reflected spots and scattering haze from said wide field fundus image; and an automated montage algorithm implemented to produce an automated montage of said plurality of retinal images into a single image of said wide field of view.
 39. The wide field fundus camera of claim 38, further comprising: a second dehazing algorithm implemented to further remove reflected and scattered light haze from said montage image.
 40. The wide field fundus camera of claim 38, wherein said objective lens is a wide field aspherical lens having a FOV of 60 degrees to 160 degrees.
 41. The wide field fundus camera of claim 38, wherein said objective lens is an ultra-wide field objective lens having a FOV of 160 degrees or wider.
 42. The wide field fundus camera of claim 38, wherein said objective lens is an ultra-wide field objective lens system comprising a contact lens, a meniscus lens and an aspherical lens.
 43. The wide field fundus camera of claim 38, wherein said real-time dehazing algorithm identifies reflected and scattered light haze in said retinal images by the position of said haze.
 44. The wide field fundus camera of claim 38, wherein said real-time dehazing algorithm identifies reflected and scattered light haze in said retinal images by spectral content of said haze.
 45. The wide field fundus camera of claim 38, wherein said plurality of illumination beam projectors comprises of 8 projectors positioned to provide eight reflection spot clusters at 12, 1:30, 3, 4:30, 6, 7:30, 9, and 10:30 o'clock positions on an eye positioned along the viewing axis.
 46. The wide field fundus camera of claim 45, wherein 4 of the 8 projectors form a first subset providing infrared illumination, and 4 of the 8 projectors form a second subset providing white light illumination, each of the first subset and the second subset being symmetrically disposed around viewing axis.
 47. The wide field fundus camera of claim 38, wherein said real-time dehazing algorithm comprises processor-accessible instructions for dehazing an image from a wide field fundus camera, that when executed perform acts comprising the steps of: computing position of Purkinje reflections from said wide field fundus camera produced by said illumination beam projectors; computing wide field fundus camera alignment with the central axis of the eye being imaged by said wide field fundus camera using the position of said Purkinje reflections within a said image from said wide field fundus camera; computing an estimated haze map for said wide field fundus image using reference ocular corneal and lens reflected and scattering haze model for said illumination beam projector at said camera alignment with said central axis of a reference model eye; computing a digital mask for removal of reflected and scattering haze from said wide field fundus image using estimated haze map; computing a processed masked wide field fundus image from said wide field fundus image by removal of portions of said wide field fundus image covered by said digital mask; computing a transmission map utilizing estimated haze map for said wide field fundus image; refining a transmission map for said wide field fundus image using reference retinal wide field fundus image; and reconstructing a retinal image from said masked wide field fundus image using the refined transmission map to dehaze the masked wide field fundus image and to produce a dehazed masked wide field retinal image.
 48. The wide field fundus camera of claim 38, wherein said real-time dehazing algorithm comprises processor-accessible instructions for dehazing an image from a wide field fundus camera, that when executed perform acts comprising the steps of: computing an estimated haze map using at least one of a reference spectrum and size and spatial distribution of said reflected and scattering haze computing a transmission map utilizing estimated haze map for said wide field fundus image; refining a transmission map utilizing estimated retinal transmission from reference retinal wide field fundus image; and reconstructing a retinal image from said wide field fundus image using the computed transmission map to dehaze the wide field fundus image and to produce a dehazed wide field retinal image.
 49. The wide field fundus camera of claim 38, wherein said automated montage algorithm comprises processor-accessible instructions for montaging sectional images from a wide field fundus camera into a single FOV wide field fundus image, that, when executed, performs acts comprising the steps of: computing position of Purkinje reflections from said wide field fundus camera produced by said illumination beam projectors computing wide field fundus camera alignment with the central axis of the eye being imaged by said wide field fundus camera using the position of said Purkinje reflections within said sectional images from said wide field fundus camera; computing an area of each said sectional image to be included in said montage image and creating a sectional image digital mask for each said sectional image to remove scattering haze and Purkinje reflections, determined by said wide field fundus camera alignment; computing a masked sectional image from said wide field fundus camera sectional image by removal of the area of each said sectional image covered by each said sectional image digital mask; computing a blending of overlapping areas of each said sectional image using one or more of sectional image exposure, wide field fundus camera alignment, sectional image haze, sectional image focus, sectional image spatial frequencies, and sectional image sharpness to preserve said montage image fine structural detail while evening out said montage image exposure to create a seamless montage; and computing an image projection for said montage image by using said wide field fundus camera alignment to minimize montage image distortion.
 50. The wide field fundus camera of claim 38, wherein said automated montage algorithm comprises processor-accessible instructions for montaging sectional images from a wide field fundus camera into a single FOV wide field fundus image, that when executed perform acts comprising the steps of: computing position of Purkinje reflections from said wide field fundus camera produced by said illumination beam projectors computing wide field fundus camera alignment with the central axis of the eye being imaged by said wide field fundus camera using the position of said Purkinje reflections within said sectional images from said wide field fundus camera; computing an estimated haze and transmission map for said wide field fundus image using reference ocular corneal and lens reflected and scattering haze model for said illumination beam projector at said camera alignment with said central axis of a reference model eye; computing a haze and transmission map directly from the wide field fundus image using spectral analysis of said illumination by said illumination beam projectors in said wide field fundus image; refining the transmission map generated by spectral analysis of said wide field fundus image utilizing the estimated transmission mask from said reference model eye for said camera alignment; computing a scoring function to rate the visibility of each pixel in each sectional retinal image using the refined transmission map; and selecting for each pixel in the output image the corresponding pixel value in the sectional retinal images having the highest visibility score.
 51. A wide field fundus camera, comprising: an objective lens having a viewing axis and disposed to form a retinal image; an image recording device disposed to capture said retinal image of said wide field of view; a plurality of eight illumination beam projectors positioned symmetrically around said viewing axis and each configured to project an illumination beam at an angle toward said objective lens; a mechanism of cross polarization configured between said image recording device and said plurality of illumination beam projectors to reject specular reflections of said illumination beams; an image display operatively coupled to the image recording device to display said retinal image from said image recording device; an electronic controller operatively coupled to said plurality of eight illumination beam projectors to provide power to each of the plurality of illumination beam projectors in a predetermined sequence to illuminate for each sequential image two of said illumination beam projectors with said illumination beam projectors positioned 180-degrees from one another around said viewing axis; and a real-time dehazing algorithm implemented to perform real-time removal of reflection and scattered light haze; an automated montage algorithm implemented to produce an automated montage of said two or four sequential retinal images into a single image of said wide field of view; and a second dehazing algorithm implemented to further remove residual reflection and scattered light haze from said automated montage image to create a haze-free montage image.
 52. The wide field fundus camera of claim 51, wherein said predetermined sequence consists of said illumination beam projectors at 12 o'clock and 6 o'clock powered for a first sequential image and said illumination beam projectors at 3 o'clock and 9 o'clock powered for a second sequential image.
 53. The wide field fundus camera of claim 51, wherein said predetermined sequence consists of said illumination beam projectors at 10:30 o'clock and 4:30 o'clock powered for a first sequential image and said illumination beam projectors at 1:30 o'clock and 7:30 o'clock powered for a second sequential image.
 54. The wide field fundus camera of claim 51, wherein said predetermined sequence consists of said illumination beam projectors at 12 o'clock and 6 o'clock powered for a first sequential image, said illumination beam projectors at 3 o'clock and 9 o'clock powered for a second sequential image, said illumination beam projectors at 10:30 o'clock and 4:30 o'clock powered for a third sequential image, and said illumination beam projectors at 1:30 o'clock and 7:30 o'clock powered for a fourth sequential image.
 55. The wide field fundus camera of claim 51, wherein said objective lens is an ultra-wide field objective lens having a FOV of 160 degrees or wider.
 56. A method of operating a wide field fundus camera, comprising the steps of: providing an objective lens having a viewing axis and disposed to image a retina having a fundus, the viewing axis being in the first alignment with the retina; providing an image recording device disposed to capture said retinal image; providing a plurality of illumination beam projectors positioned around said viewing axis and projected each at a predetermined angle with respect to said viewing axis; providing a mechanism of cross polarization configured between said image recording device and said plurality of illumination beam projectors to reject specular reflections of said illumination beams; providing an image display configured to display said retinal image from said image recording device; providing a computing processor coupled with said image recording device and said image display to enable real-time image processing and display; providing a real-time dehazing algorithm incorporated in said computing processor to perform real-time removal of reflection and scattered light haze; providing an electronic controller powering said plurality of illumination beam projectors in a programmable manner; capturing a plurality of fundus images at the first alignment, each image captured with the plurality of illumination beam projectors in a corresponding state of illumination, at least two of the states of illumination being different than one another; and providing an automated montage algorithm incorporated in said computing processor to perform an automated montage of said plurality of retinal images into a single montage image of said wide field of view.
 57. The method of claim 56, further comprising the steps of: providing a dehazing algorithm incorporated in said computing processor to further remove reflected and scattered light haze from said montage image. 